A remarkable mantra from the Yajur Veda. It is also in Bṛhadāraṇyaka Upaniṣad 1.3.28

असतोमा सद्गमय।
तमसोमा ज्योतिर् गमया।
मृत्योर्मामृतं गमय॥

Aum
Asato mā sad gamaya
Tamaso mā jyotir gamaya
Mṛtyormā amṛtam gamaya
Aum śānti śānti śāntiḥ

meaning:

Aum
from non-truth lead me to truth
from darkness lead me to light
from death lead me to immortality

peace, peace,peace

Om Tryambakam Yajamahe
Sugandhim Pushtivardhanam
Urvarukamiva Bandhanan
Mrityor Mukshiya Maamritat

We Meditate on the Three-eyed reality
Which permeates and nourishes all like a fragrance.
May we be liberated from death for the sake of immortality,
Even as the cucumber is severed from bondage to the creeper.

Description:

The Mahamrityunjaya Mantra (Sanskrit: महामृत्युंजय मंत्र, Mahāmṛtyuṃjaya Mantra ”great death-conquering mantra”), also called the Tryambakam Mantra, is a verse of the Rigveda (RV 7.59.12). It is addressed to Tryambaka “the three-eyed one”, an epithet of Rudra, later identified with Shiva. The verse also recurs in theYajurveda (TS 1.8.6.i; VS 3.60)

sources: http://en.wikipedia.org/wiki/Mahamrityunjaya_Mantra

This mantra is one of the more potent of the ancient Sanskrit mantras. Maha mrityunjaya is a call for enlightenment and is a practice of purifying the karmas of the soul at a deep level. It is also said to be quite beneficial for mental, emotional, and physical health.